The present invention relates to a radiation emitting device, and more particularly, to a system and method for evaluating beam quality during therapy using electronic portal imaging.
Radiation emitting devices are generally known and used, for instance, as radiation therapy devices for the treatment of patients. A radiation therapy device generally includes a gantry which can be swiveled around a horizontal axis of rotation in the course of a therapeutic treatment. A linear accelerator is located in the gantry for generating a high energy radiation beam for therapy. This high energy radiation beam can be an electron beam or photon (X-ray) beam. During treatment, this radiation beam is trained on one zone of a patient lying in the isocenter of the gantry rotation.
Prior to receiving therapeutic doses of radiation, the patient must be positioned accurately and precisely. Radio-therapists have historically used laser pointers and radiographic film to ensure that patients are properly positioned. This can be a complex and time-consuming process. Electronic portal imaging devices (EPIDs) can now accomplish this step much more rapidly by providing instantaneous radiographic imaging on a computer monitor. Emerging applications for EPIDs require (1) accurate and precise positioning of the EPID, (2) adequate clearance between the EPID and the patient or treatment table, and (3) maneuverability of the EPID across a sufficiently wide range of motion.
A radiation therapy apparatus according to an embodiment of the present invention includes a portal imaging device having a portal imaging device positioner for accurately positioning the EPID, providing sufficient clearance, and maneuverability across a wide range of motion.
A portal imaging device positioning apparatus according to an embodiment of the present invention includes a portal imaging device positioner attachable to a support such as a telescoping boom. The portal imaging device positioner is adapted to vertically adjust an imaging panel in either a treatment or dosimetry mode to receive radiation that has passed through a body in the patient plane, and adjust the panel in a physics mode to receive radiation at the patient plane.
The portal imaging device positioner includes an imaging panel vertically attachable to a mounting unit which in turn is vertically attachable to a main vertical drive unit. The main vertical drive unit attaches adjustably to the telescoping boom. The mounting unit includes one or more hinges for deploying the imaging panel to a horizontal position. The main vertical drive unit includes a mounting cavity on a side adjacent the telescoping boom. The main vertical drive unit is adjustable relative the telescoping boom to at least first and second positions within the mounting cavity.
A controller for the portal imaging device implements a graphical user interface that allows the position of the imaging panel to be adjusted using buttons identified with symbols to indicate the direction of motion. The interface allows positions to be stored and recalled such that the positioner moves to the desired position upon recall. Commands and sensor data are exchanged between the treatment unit and the portal imaging device controller to allow motions of the portal imaging positioner to be coordinated with other portions of the treatment unit.
In one embodiment of the present invention, the controller defines a bounding box around an X-ray field, which is then superimposed on an imaging area. If the bounding box exceeds the bounds of the imaging area, then an alarm may be provided to alert-the user, or other action may be undertaken.